Field of the Invention
The present invention relates to a sheet discharge apparatus for discharging a sheet from between a discharge roller and a feeding roller as well as to an image forming apparatus, such as copiers, printers, facsimiles and machines with multi-functional peripherals, which employs such a sheet discharge apparatus.
Description of the Related Art
In the image forming apparatus such as copiers, printers, facsimiles and machines with multi-functional peripherals, the sheet discharge apparatus is used for sequentially discharging sheets with toner images formed thereon to a sheet delivery portion.
The sheet discharge apparatus commonly operates as follows to sequentially discharge the sheets with toner images formed thereon to the sheet delivery portion. The sheet with the toner image formed thereon is guided into nip between the discharge roller and the feeding roller. With this sheet pinched between roller portions of the discharge roller and roller portions of the feeding roller, the discharge roller and the feeding roller are rotated to discharge the sheet from between the discharge roller and the feeding roller.
In the case where the sheet is discharged from between the discharge roller and the feeding roller in this manner, resistance is applied to the discharged sheet because the sheet is discharged from between the discharge roller and the feeding roller while making contact with an upper surface of the sheet delivery portion or the sheet already discharged.
In a case where a sheet having high frictional resistance, a sheet elongated in a sheet discharge direction, or a sheet curled during thermal fixing of the toner image or the like is discharged, or where a sheet is discharged at low velocity, a trailing end of the discharged sheet may sometimes remain on the roller portions of the feeding roller so that the sheet is not properly discharged from between the discharge roller and the feeding roller onto the sheet delivery portion.
If the trailing end of the discharged sheet remains on the roller portions of the feeding roller, the following problem may occur. When the next sheet is discharged from between the discharge roller and the feeding roller, the preceding sheet remaining on the roller portions of the feeding roller may become an obstacle to the discharge of the next sheet, which is not discharged but gets jammed. Otherwise, the preceding sheet remaining on the roller portions of the feeding roller may be pushed out significantly by the next sheet discharged, thus significantly displaced from a discharge position. Otherwise, the next sheet may get under the preceding sheet remaining on the roller portions of the feeding roller, causing the collapse of the order of discharged sheets.
In this connection, Patent Document 1 (Japanese Unexamined Patent Publication No. 2002-114423) has heretofore proposed an arrangement where a pressing member is rotatably arranged in a manner to block a sheet discharge path for a sheet discharged from between the discharge roller and the feeding roller. This pressing member is pushed up by the sheet discharged from between the discharge roller and the feeding roller so as to allow the sheet to be discharged to the sheet delivery portion. Further, the pressing member presses down the trailing end of the sheet passed through between the discharge roller and the feeding roller so as to separate the trailing end of the sheet from the feeding roller.
However, in the case where the pressing member is rotatably arranged to block the sheet discharge path such that the pressing member is pushed up by the sheet discharged from between the discharge roller and the feeding roller, a problem exists that a sheet weak in stiffness has difficulty in adequately pushing up the pressing member so as to get jammed at this pressing member. On the other hand, in a case where the above-described pressing member is adapted to be easily pushed up by the discharged sheet, a problem exists that this pressing member is incapable of adequately pressing down the trailing end of the sheet passed through between the discharge roller and the feeding roller. It is difficult for the pressing member to adequately separate the trailing end of the sheet from the feeding roller.
Further, Patent Document 2 (Japanese Unexamined Patent Publication No. 2005-263335) has heretofore proposed an arrangement which employs a pressing member including first and second arms. The sheet transported through between a first pair of discharge rollers rotates the pressing member to retract down the first arm of the pressing member. The sheet is moved over the first arm thus retracted and guided in between a second pair of discharge rollers on a downstream side. This sheet is discharged from between the second pair of discharge rollers to the sheet delivery portion outside an image forming apparatus. In the meantime, the second arm of the rotatable pressing member is rotated toward the outside of the image forming apparatus so that this second arm presses down the trailing end of the sheet discharged to the sheet delivery portion outside the image forming apparatus.
However, the arrangement disclosed in Patent Document 2 also has the problem that since the sheet transported through between the first pair of discharge rollers rotates the pressing member so as to retract down the first arm of the pressing member, as described above, the sheet weak in stiffness has difficulty in adequately rotating the pressing member, getting jammed at this first arm. Further, in the arrangement disclosed in Patent Document 2, the second arm of the pressing member is simply arranged to press down the trailing end of the sheet discharged to the sheet delivery portion outside the image forming apparatus. In the case of a sheet with the trailing end remaining in between the second pair of discharge rollers, therefore, it is also difficult for the second arm to adequately separate this sheet from between the second pair of discharge rollers.